Cretaceous‐Cenozoic lithostratigraphy of the Chatham Islands

Abstract

Abstract New mapping on the Chatham Islands, coupled with many new fossil determinations, has significantly refined our understanding of stratigraphic relationships of the Cretaceous‐Cenozoic rocks exposed there. The following units are recognisable: Waihere Bay Group (emended), Tupuangi Formation (redefined; 240‐400 m; Late Albian‐Santonian), Pitt Island Group (emended), Kahuitara Tuff (< 225 m; Campanian‐Maastrichtian), Southern Volcanics (> 300 m; Campanian‐Maastrichtian), unnamed Cretaceous sandstone (> 0.3 m; Late (?) Cretaceous), unnamed Haumurian limestone (fissure fills; Late Maastrichtian), Tioriori Group (emended), Takatika Grit ( c . 6 m; Maastrichtian‐Paleocene), Tutuiri Greensand (< 25 m; Late Paleocene), Tumaio Limestone Member (new unit; c . 8 m; Late Paleocene), Kekerione Group (emended), Red Bluff Tuff (> 100 m; Late Paleocene‐Early Eocene), Te Whanga Limestone (redefined; 40‐60 m; Early Eocene‐Early Oligocene), Matanginui Limestone Member (redefined; < 35 m; Early‐ Late Eocene), Te One Limestone Member (redefined; > 25 m; Late Eocene‐Early Oligocene), Northern Volcanics (emended; < 140 m; Late Eocene?‐Early Oligocene?), Victoriella Limestone Lithofacies (new unit; < 3 m; Early Oligocene), Taoroa Limestone Lithofacies (new unit; c . 3 m; Early Miocene), unnamed Altonian tuff ( c . 0.15 m; Early Miocene), unnamed Altonian limestone (< 5 m; Early Miocene), Mairangi Group (new name), Rangitihi Volcanics (< 100 m; Late Miocene?‐Early Pliocene), Momoe‐a‐toa Tuff (< 120 m; Early Pliocene), Rangiauria Breccia (emended; < 300 m; Late Miocene), Motarata Limestone (new unit; > 5 m; Pliocene) Onoua Limestone (emended; > 26 m; Pliocene), unnamed Waipipian limestone ( c . 1 m; Late Pliocene), Whenuataru Tuff (< 50 m; Early‐Late Pliocene), Mangere Formation (emended; c . 52 m; Late Pliocene), Pyramid Phonolite (> 174 m; Late Pliocene), unnamed Pliocene volcanics (> 150 m; Early Pliocene), Karewa Group (new unit), Titirangi Sand (emended; c . 6 m; Late Pliocene). Many of these units are very limited in extent but their recognition is considered important for discussions on the geological history and interpretation of the Chatham Islands — Chatham Rise region.